My tap water is pretty soft (definitely softer than what my pool pro original set my CH at). When I fill my pool from evap, it tends to flow out the overflow for a while before I catch it. This combined with use and splashing out and rain causing it to flow out the overflow has lowered CH over time.
Can adding a lot of calcium chloride at once reduce FC??
- Thread starter Bobkam
- Start date
Also, another anecdotal point. Even though my FC has been decreasing after adding the CH, my ORP reading went from 690mV to 790mV and has slowly been dropping. After 48 hours, it’s at 710mV. I know that the general consensus on ORP and IntelliChem isn’t great and I don’t use it as a measurement, but more of an observation - I have been able to correlate ORP to FC level generally speaking. It seems counter for ORP to increase if FC is decreasing. I can only assume that the CH is effecting the probes measurement. Just thought I would add that note.
That may also be an indication that whatever the impurity is maybe affects the FC test instead of FC itself. Very helpful info.
As this interesting subject continues, I would ask that responders use REAL numbers. "kinda' low", "off the charts", "higher than it's ever been" are not really helpful. They just don't move the discussion forward.
This same idea spills over into ALL areas of TFP, Newbies in particular, are guilty of generalizations from which we can gain very little. Test results with fairly precise testing are a cornerstone to a TFP pool. Let's challenge ourselves to be exact when possible and to pass that along to the newbies who are learning about what we teach.
This same idea spills over into ALL areas of TFP, Newbies in particular, are guilty of generalizations from which we can gain very little. Test results with fairly precise testing are a cornerstone to a TFP pool. Let's challenge ourselves to be exact when possible and to pass that along to the newbies who are learning about what we teach.
More anecdotal add-ons as I continue to chase this. I’ve been running my SWCG at 70% since yesterday at noon. Testing this morning revealed 3.0ppm Chlorine with .5ppm combined chlorine, so I bumped up the SWCG to 100% and tested again this afternoon - chlorine level of 3.6ppm and 0.2ppm of combined chlorine. Honestly, I don’t know what this really means other than after adding the CH, chlorine went to work and was used up by something which is evident in the combined chlorine level. I am contemplating whether to SLAM or not. I assume no if combined chlorine reduces? Any thoughts on this?
kyndacrazy
I'd recommend you do a OCLT before you jump to conclusions.
I'd recommend you do a OCLT before you jump to conclusions.
I used a new bag of clorox calcium hardness 4lb, no chlorine loss, but also no calcium increase... lost $11. Today I added approximately 7.5lb of Leslie calcium hardness I found in my shed. It's been there for several years. I haven't checked my calcium yet, but my chlorine is usually 3.5 every evening and today it's 1. It hasn't been that low in years! Something is up with adding calcium hardness and losing chlorine, just sayin
4 pounds of calcium isn’t going to add much to an 18k gallon pool. Maybe not even measurable with the kit so probably wasn’t a waste.
If your chlorine is that low normally (3.5ppm) you may have something else going on.
If your chlorine is that low normally (3.5ppm) you may have something else going on.
Did you use the entire rest of the bag of the Leslie’s or do you have any left? A bucket test with a control might give some initial useful data. I’d suggest something really easy for anyone to actually do as a first test. Two five gallon buckets with about four gallons of pool water in each. Place in a shaded area (garage would seem convenient). Test FC and CH in each — heck, might as well test pH, TA and CYA too, easy enough — see exactly what changes. Add one tablespoon of the suspect calcium chloride to one of the buckets and stir. Wait 24 hrs. Retest both buckets and see what changed.
Out of the sun. Fewer variables that may affect FC, the better. Hope is FC reduced in test bucket and no change in control. If that happens, then we need to devise tests on the substance itself. The other tests besides just FC might give also someone an insight.
If no change in shade, then maybe a test in full sun to see if sun has anything to do with it all?
I’m betting on an ammonia compound as an impurity — good a guess as any
- Mar 5, 2020
- 3,056
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
I did a bucket test. Used Hy-Clor Calcium Increaser from our local Hardware store. Also bought two new buckets. Filled them with 8L of pool water (11.6°C or 53°F, still winter here). FC in both buckets 9ppm, CC below 0.5ppm, CH 375ppm, CYA 50ppm.
Then I added about 2.1g of Calcium Increaser to one bucket. For this brand I usually assume a mix of 1/3 anhydrous and 2/3 dihydrate, so that should increase CH by about 200ppm.
I tested the water about 15min, 40min and 13h (next morning) after the addition. CH confirmed at 575ppm as expected.
In the reference sample, FC remained pretty much unchanged at 9ppm, no change in CC as well (wouldn't make sense anyway with FC unchanged).
In the Calcium Increaser sample, there was an initial small drop to FC 8.5ppm, no change in CC. That number remained constant until the final measurement in the morning.
All in all a small effect (0.5ppm decrease in FC) after a significant addition of Calcium Chloride (the amount I added would be equivalent to adding nearly 18kg to my 66kL pool, nothing I would ever recommend doing). Normally, I would increase my CH in 25ppm steps, where the FC decrease should scale down to less than 0.1ppm, pretty much not detectable.
Then I added about 2.1g of Calcium Increaser to one bucket. For this brand I usually assume a mix of 1/3 anhydrous and 2/3 dihydrate, so that should increase CH by about 200ppm.
I tested the water about 15min, 40min and 13h (next morning) after the addition. CH confirmed at 575ppm as expected.
In the reference sample, FC remained pretty much unchanged at 9ppm, no change in CC as well (wouldn't make sense anyway with FC unchanged).
In the Calcium Increaser sample, there was an initial small drop to FC 8.5ppm, no change in CC. That number remained constant until the final measurement in the morning.
All in all a small effect (0.5ppm decrease in FC) after a significant addition of Calcium Chloride (the amount I added would be equivalent to adding nearly 18kg to my 66kL pool, nothing I would ever recommend doing). Normally, I would increase my CH in 25ppm steps, where the FC decrease should scale down to less than 0.1ppm, pretty much not detectable.
- May 23, 2015
- 24,438
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
That 0.5ppm change is within the limits of the test too so, in reality, the test results are technically inconclusive. But still worthwhile doing. Thanks.
- Mar 5, 2020
- 3,056
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
Agree, pretty much within the test tolerances. But quite consistent. I used a syringe to get the sample volumes as reproducible as possible, and then tested three times 8.5ppm in the CaCl2 sample and three times 9ppm in the reference sample.
Orion7319
Well-known member
- Jul 1, 2020
- 1,288
- Pool Size
- 19775
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Interesting thread, and this is completely speculative on my part. Reading though this thread it sounds like it’s only affecting people with salt water generators. Curious what salt water generators the affected people have and how they added the calcium to the pool. Did they dump it into the deep end near their drains? Was it broadcast or dissolved first?
I spread mine around the deep end. But did it at night a couple hours before my pump turned off - so in my case it wasn’t a result of the swg being “disabled” temporarily.
I’ll just add to the conversation and the growing library of anecdotal evidence. My neighbor (no SWG in her pool) told me after adding CH increaser to her pool that her FC was demolished. I thought she was crazy or maybe had made a mistake on testing. I was about to add 25 lbs of CH increaser so I measured my FC before at 3.0, and after it was 0.5!
I can’t speak to why, but I can tell you unequivocally my FC was consumed after adding CH increaser (and changing nothing else).
Maybe it’s something about the product we used because we both used the same thing.
Attaching a file of the CH increaser we used.
I can’t speak to why, but I can tell you unequivocally my FC was consumed after adding CH increaser (and changing nothing else).
Maybe it’s something about the product we used because we both used the same thing.
Attaching a file of the CH increaser we used.
Attachments
FC drop happened to me, twice this week, when adding “Poolife Calcium Plus” to get CH up from 80ppm.
Added 20 pounds via broadcasting in deep end, mostly near a jet.
First time:
FC was 3.5 immediately before addition, and then two hours after, it was 2.0. This was in the evening when the sun was behind trees for the last couple hours of the day.
Second time:
FC went from 4.0 to 2.5. We swam 4 hours after addition, and the pungent public pool smell was there to everyone who swam, and we never had that smell in our pool before.
I did a CC test after we swam, and it was 0. I suspect whatever is reacting with FC in these bags isn’t what we’d typically expect to drop FC (eg not ammonia).
Added 20 pounds via broadcasting in deep end, mostly near a jet.
First time:
FC was 3.5 immediately before addition, and then two hours after, it was 2.0. This was in the evening when the sun was behind trees for the last couple hours of the day.
Second time:
FC went from 4.0 to 2.5. We swam 4 hours after addition, and the pungent public pool smell was there to everyone who swam, and we never had that smell in our pool before.
I did a CC test after we swam, and it was 0. I suspect whatever is reacting with FC in these bags isn’t what we’d typically expect to drop FC (eg not ammonia).